Disable Second CPU for longer battery life?

For anyone with a Core Duo based laptop - If you disable one of the processor cores will you get longer battery life? I've seen it in some Toshiba's bios that you can disable one core - typical 3.5hours is a little short for usage in classes but if I can get like 4-6 that would be better.

From what I've seen it's better to leave both cores on. The load balancing between the cores uses less energy then full usage of one core. At least that's how it is on the MacBooks/Pro.

Yeah, I was afraid of that.